1. Field of the Invention
The present invention relates to a wheelchair which is configured such that the vehicle width can be varied by attaching/detaching rear wheels.
2. Description of the Related Art
In general, a wheelchair of this kind includes a vehicle frame which is provided with a seat section and a back section, front wheels are provided at a lower portion of a front end part of the vehicle frame, and rear wheels, which are larger in size than the front wheels, are provided on both sides of a rear end part of the vehicle frame. Hand rims, which are slightly smaller in diameter than the rear wheels, are provided on the outside of the rear wheels, so that a user who sits on the seat section can manually rotate the rear wheels.
If the rear wheels with the hand rims are provided on the outside in the width direction of the vehicle frame, the vehicle width of the wheelchair increases. Consequently, the driving of the wheelchair becomes difficult in a narrow place, for example, in a room or in a train.
Taking this into account, the rear wheels are provided to be attachable/detachable to/from the vehicle frame, and lift-up wheels are provided at a lower portion of a rear end part of the vehicle frame such that the lift-up wheels can be elevated. When the rear wheels are to be used, the lift-up wheels are raised so that the lift-up wheels may not come in contact with the ground. When the rear wheels are detached and the wheelchair is used with a reduced vehicle width, the lift-up wheels are lowered and put in contact with the ground.
Thereby, when the wheelchair is driven in a narrow place, for instance, in a room or in a train, the vehicle width is reduced by detaching the rear wheels, and the lift-up wheels are lowered. Thereby, the vehicle frame is supported to be movable by the front wheels and lift-up wheels.
In the prior art, in the wheelchair with the above-described structure, universal casters, which are rotatable not only about a horizontal axis but also about a vertical axis, are used for the front wheels, so that the direction of the vehicle can easily be turned when the wheelchair is moved by pushing hand-push handles which are provided on the back section. However, fixed casters, which can rotate about only the horizontal axis of the horizontal axis and vertical axis, have been used for the lift-up wheels, like the rear wheels.